I was playing Minecraft Preview in a world called Test1. I was doing a bit of experimentation, so I generated some snnifers to test their AI. The fact is that I decided to test the collisions to see if they moved when I hit them. Yes, they moved, but it could go through his body. This not only happens to the player, but affects all mobs. And it is that after having tested the collision, another snnifer transferred it, making a kind of Z fighting.